1. Field of the Invention
The present invention relates to a combustion engine, in particular to a combustion engine with a valvetrain. In particular, the present invention relates to a combustion engine with a valvetrain with variable valve control.
Typically, in combustion engines, valvetrains are provided that generate a valve lift of fixed lift height and duration using a camshaft. The inflow by volume of the air fuel mixture is controlled by a throttle valve. Such a valvetrain, however, has disadvantages regarding an optimal adjustment to different load regimes of the combustion engine. Such disadvantages can at least partially be avoided by a valvetrain of variable valve lift.
2. Description of the Related Art
Valvetrains with variable valve lift are known in the art. The Valvetronic system of BMW, for example, is a valvetrain with variable valve lift, which is being produced in series. It allows a variable adjustment of valve lift and duration of valve opening in response to a number of drive parameters, such as rotational speed and the position of the throttle control. Further, valvetrains with variable valve lift are known for motors of low rotational speed with cam in block. Cam-in-block motors, however, generally have a number of disadvantages, in particular in the regime of high rotational speed. For example, relatively large masses generally need to be moved when opening and closing the valve.
Further, EP 1 350 928 describes an apparatus for smoothly varying the valve lift in combustion engines. Therein, a linear cam is pushed more or less deeply between two rollers by an actuating member, wherein one of the rollers is movable in the sense of the valve lift. Thereby, a lift curve on a roller, mounted in a rocker level or another actuating member towards the valve, actuates the valve lift.
A further valvetrain for a combustion engine is described In U.S. Pat. No. 5,357,915. The valvetrain described therein allows modifying the valve synchronization and the valve lift of the intake and exhaust valves, which are driven by rocker arms and overhead camshafts.
PCT 2002/053881 describes a variably adjustable mechanical valve gear for a gas-reversing valve with a closing spring on a piston engine, in particular a piston-type internal combustion engine, comprising a driving mechanism for generating a lifting movement that is effective counter to the force of the closing spring on the gas-reversing valve and a stroke transfer means arranged between the driving mechanism and the gas-reversing valve, which acts upon the gas-reversing valve in the direction of its movement axis and for which the stroke distance can be adjusted in the direction of the movement axis via an adjustable guide element and which is realized with a pivoting element that is connected with its end facing away from the gas-reversing valve to the driving mechanism and is guided so as to pivot back and forth on the guide element designed as control curve.
Further, FR 1 284 700 describes a valvetrain for combustion engines, which allows to adjust automatically the duration of the valve lift and the lifting height of the valves, in order to adapt them to the rotational speed.
A valvetrain for a motor according to EP 1 515 008 is composed as follows: An intermediate rocking element is interposed between a pivoting earn surface and a rocking surface of a rocking arm. By shifting of contact spots an opening duration and an opening height of the valve can be adjusted continuously.
DE 23 35 634 relates to a valve adjustment for combustion engines, comprising a driving shaft, an arrangement for transforming the rotational movement to a pivotal movement actuating the valve, and an arrangement for modifying the valve lift in response to the rotational speed and the load of the combustion engine.
U.S. Pat. No. 6,684,832 describes a valvetrain of a combustion engine, which allows modifying the lift and the opening and closing angle. To this purpose, the camshaft is not mounted fixedly on the cylinder head, but it oscillates about an axis, and by this oscillation the valve lift and duration of valve opening are modified.
The valvetrains mentioned above, however, are deficient in several respects, for example regarding their space requirements, their weight, susceptibility to wear, and limitations of the variability of the valve control.
The present invention attempts to reduce at least some of the above-mentioned problems. Further, the present invention attempts to provide a combustion engine, which has good properties with respect to motor performance, wear, and/or other aspects. The object is solved by a combustion engine according to independent claim 1. Further advantages, features, aspects and details of the invention as well as preferred embodiments and particular aspects of the invention are evident from the dependent claims, the description and the drawings.